Breast cancer patients could be spared chemotherapy with new genetic test, study shows

It’s a gruelling decision every breast cancer patient and their doctor must consider: do we need to start chemotherapy, or could we spare you the ravages of the toxic, yet potentially life-saving treatment?

A genetic test could see thousands of Australian women with early-stage breast cancer safely avoid chemotherapy, a landmark trial shows.

Based the genetic profile of their tumours, nearly half of women (46 per cent) with early-stage breast cancer who are at high clinical risk of the cancer returning may not require chemo, found one of the largest and most robust studies of genetic testing published.

The trial investigated whether the test (dubbed MammaPrint in Europe and Australia) could identify which patients had a low genetic risk of their cancer re-emerging among women in the early stages of the most common type of breast cancer: HER2 negative tumours.

Associate Professor Guy Hingston wants all women with breast cancer about to undergo chemo to have access to Mammaprint. Photo: Supplied

Researchers screened more than 6600 patients and found 1550 had a high clinical risk, but low genetic risk, of their cancer returning.

Women deemed to have a high clinical risk of recurrence are usually treated with chemo.

The researchers randomly assigned these women to chemo treatment or no chemo after their first-line treatments (surgery, hormone therapy and radiation).

After five years, 94.4 per cent of the women who did not receive chemo had no distant metastasis; their cancer hadn’t spread, found the study published in the New England Journal of Medicine on Thursday.

There was only 1.5 percentage points that separated them from the women who did receive chemo, with 95.9 per cent of these patients showing no distant metastasis at the five-year mark.

“We found that chemotherapy with its toxic effects could be avoided in these patients,” the authors concluded. They plan to follow the women for another five years to document their ongoing survival rates.

“Given these findings, approximately 46 per cent of women with breast cancer who are at high clinical risk might not require chemotherapy, they said.

The risks from certain types of chemo increase with the patient’s age. The risk of leukemia is about 0.5 per cent to 1 per cent, and the heart risk can reach 4 per cent or 5 per cent in older women, Dr Freedman said.

Australian oncologist Associate Professor Guy Hingston – who pioneered access to MammaPrint for Australian women – recommended all Australian women who were about to undergo chemo should check with their oncologist to see if they would benefit from the test.

Between 4000 and 5000 Australian women diagnosed with breast cancer every year would be eligible for the test. The study results suggest roughly 2000 to 2500 women could be spared chemo every year.

“We now live and work in a different world of breast cancer management. Women already shattered with a new diagnosis of breast cancer, should not needlessly be put through chemotherapy, if genomically their cancer can be shown to have a low risk of recurrence,” Associate Professor Hingston said.

“As a medical profession, we are here to help women, not hurt them, and this form of genomic testing is a great step forward in our ability to more accurately target treatment and provide personalised cancer therapy.”

But MammaPrint is not universally accessible. Australian samples are sent to Los Angeles for testing and come with an out of pocket cost of roughly $5500 in Australia.

The medical services advisory committee is assessing an application for government funding.

A sobering editorial published alongside the study findings warned the trial was not the final proof that chemotherapy could be tossed aside for this group of patients.

“The immediate question for many observers is this: Was withholding chemotherapy in such patients actually safe?” wrote Drs Clifford Hudis and Maura Dickler at the Memorial Sloan Kettering Cancer Center, New York.

“[A] difference of 1.5 percentage points, if real, might mean more to one patient than to another.

“What doctors and their patients do with the results of such testing will be highly individualised — and will inevitably be finessed by the findings from future studies,” they wrote.